QByteArray 類

QByteArray 類提供字節數組。更多...

頭：	#include <QByteArray>
CMake:	find_package(Qt6 REQUIRED COMPONENTS Core) target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake:	QT += core

所有成員列錶，包括繼承成員
Deprecated members
QByteArray is part of 隱式共享類 and 用於字符串數據的類 .

注意： 此類的所有函數可重入 .

公共類型

class	FromBase64Result
enum	Base64Option { Base64Encoding, Base64UrlEncoding, KeepTrailingEquals, OmitTrailingEquals, IgnoreBase64DecodingErrors, AbortOnBase64DecodingErrors }
flags	Base64Options
	const_iterator
	const_reverse_iterator
	iterator
	reverse_iterator

公共函數

	QByteArray ()
	QByteArray (const char * data , qsizetype size = -1)
	QByteArray (qsizetype size , char ch )
	QByteArray (qsizetype size , Qt::Initialization)
	QByteArray (const QByteArray & other )
	QByteArray (QByteArray && other )
	~QByteArray ()
QByteArray &	append (const QByteArray & ba )
QByteArray &	append (char ch )
QByteArray &	append (qsizetype count , char ch )
QByteArray &	append (const char * str )
QByteArray &	append (const char * str , qsizetype len )
QByteArray &	append (QByteArrayView data )
char	at (qsizetype i ) const
char	back () const
char &	back ()
QByteArray::iterator	begin ()
QByteArray::const_iterator	begin () const
qsizetype	capacity () const
QByteArray::const_iterator	cbegin () const
QByteArray::const_iterator	cend () const
void	chop (qsizetype n )
QByteArray	chopped (qsizetype len ) const
void	clear ()
int	compare (QByteArrayView bv , Qt::CaseSensitivity cs = Qt::CaseSensitive) const
QByteArray::const_iterator	constBegin () const
const char *	constData () const
QByteArray::const_iterator	constEnd () const
bool	contains (QByteArrayView bv ) const
bool	contains (char ch ) const
qsizetype	count (QByteArrayView bv ) const
qsizetype	count (char ch ) const
QByteArray::const_reverse_iterator	crbegin () const
QByteArray::const_reverse_iterator	crend () const
char *	data ()
const char *	data () const
QByteArray::iterator	end ()
QByteArray::const_iterator	end () const
bool	endsWith (QByteArrayView bv ) const
bool	endsWith (char ch ) const
QByteArray::iterator	erase (QByteArray::const_iterator first , QByteArray::const_iterator last )
QByteArray::iterator	erase (QByteArray::const_iterator it )
QByteArray &	fill (char ch , qsizetype size = -1)
QByteArray	first (qsizetype n ) const
char	front () const
char &	front ()
qsizetype	indexOf (QByteArrayView bv , qsizetype from = 0) const
qsizetype	indexOf (char ch , qsizetype from = 0) const
QByteArray &	insert (qsizetype i , QByteArrayView data )
QByteArray &	insert (qsizetype i , const char * s )
QByteArray &	insert (qsizetype i , const QByteArray & data )
QByteArray &	insert (qsizetype i , qsizetype count , char ch )
QByteArray &	insert (qsizetype i , char ch )
QByteArray &	insert (qsizetype i , const char * data , qsizetype len )
bool	isEmpty () const
bool	isLower () const
bool	isNull () const
bool	isUpper () const
bool	isValidUtf8 () const
QByteArray	last (qsizetype n ) const
qsizetype	lastIndexOf (QByteArrayView bv , qsizetype from ) const
qsizetype	lastIndexOf (char ch , qsizetype from = -1) const
qsizetype	lastIndexOf (QByteArrayView bv ) const
QByteArray	left (qsizetype len ) const
QByteArray	leftJustified (qsizetype width , char fill = ' ', bool truncate = false) const
qsizetype	length () const
QByteArray	mid (qsizetype pos , qsizetype len = -1) const
QByteArray	percentDecoded (char percent = '%') const
QByteArray &	prepend (QByteArrayView ba )
QByteArray &	prepend (char ch )
QByteArray &	prepend (qsizetype count , char ch )
QByteArray &	prepend (const char * str )
QByteArray &	prepend (const char * str , qsizetype len )
QByteArray &	prepend (const QByteArray & ba )
void	push_back (const QByteArray & other )
void	push_back (char ch )
void	push_back (const char * str )
void	push_back (QByteArrayView str )
void	push_front (const QByteArray & other )
void	push_front (char ch )
void	push_front (const char * str )
void	push_front (QByteArrayView str )
QByteArray::reverse_iterator	rbegin ()
QByteArray::const_reverse_iterator	rbegin () const
QByteArray &	remove (qsizetype pos , qsizetype len )
QByteArray &	removeAt (qsizetype pos )
QByteArray &	removeFirst ()
QByteArray &	removeIf (Predicate pred )
QByteArray &	removeLast ()
QByteArray::reverse_iterator	rend ()
QByteArray::const_reverse_iterator	rend () const
QByteArray	repeated (qsizetype times ) const
QByteArray &	replace (qsizetype pos , qsizetype len , QByteArrayView after )
QByteArray &	replace (qsizetype pos , qsizetype len , const char * after , qsizetype alen )
QByteArray &	replace (char before , QByteArrayView after )
QByteArray &	replace (const char * before , qsizetype bsize , const char * after , qsizetype asize )
QByteArray &	replace (QByteArrayView before , QByteArrayView after )
QByteArray &	replace (char before , char after )
void	reserve (qsizetype size )
void	resize (qsizetype size )
void	resize (qsizetype newSize , char c )
QByteArray	right (qsizetype len ) const
QByteArray	rightJustified (qsizetype width , char fill = ' ', bool truncate = false) const
QByteArray &	setNum (int n , int base = 10)
QByteArray &	setNum (short n , int base = 10)
QByteArray &	setNum (ushort n , int base = 10)
QByteArray &	setNum (uint n , int base = 10)
QByteArray &	setNum (long n , int base = 10)
QByteArray &	setNum (ulong n , int base = 10)
QByteArray &	setNum (qlonglong n , int base = 10)
QByteArray &	setNum (qulonglong n , int base = 10)
QByteArray &	setNum (float n , char format = 'g', int precision = 6)
QByteArray &	setNum (double n , char format = 'g', int precision = 6)
QByteArray &	setRawData (const char * data , qsizetype size )
void	shrink_to_fit ()
QByteArray	simplified () const
qsizetype	size () const
QByteArray	sliced (qsizetype pos , qsizetype n ) const
QByteArray	sliced (qsizetype pos ) const
QList<QByteArray>	split (char sep ) const
void	squeeze ()
bool	startsWith (QByteArrayView bv ) const
bool	startsWith (char ch ) const
void	swap (QByteArray & other )
QByteArray	toBase64 (QByteArray::Base64Options options = Base64Encoding) const
CFDataRef	toCFData () const
double	toDouble (bool * ok = nullptr) const
emscripten::val	toEcmaUint8Array ()
float	toFloat (bool * ok = nullptr) const
QByteArray	toHex (char separator = '\0') const
int	toInt (bool * ok = nullptr, int base = 10) const
long	toLong (bool * ok = nullptr, int base = 10) const
qlonglong	toLongLong (bool * ok = nullptr, int base = 10) const
QByteArray	toLower () const
NSData *	toNSData () const
QByteArray	toPercentEncoding (const QByteArray & exclude = QByteArray(), const QByteArray & 包括 = QByteArray(), char percent = '%') const
CFDataRef	toRawCFData () const
NSData *	toRawNSData () const
short	toShort (bool * ok = nullptr, int base = 10) const
std::string	toStdString () const
uint	toUInt (bool * ok = nullptr, int base = 10) const
ulong	toULong (bool * ok = nullptr, int base = 10) const
qulonglong	toULongLong (bool * ok = nullptr, int base = 10) const
ushort	toUShort (bool * ok = nullptr, int base = 10) const
QByteArray	toUpper () const
QByteArray	trimmed () const
void	truncate (qsizetype pos )
const char *	operator const char * () const
const void *	operator const void * () const
bool	operator!= (const QString & str ) const
QByteArray &	operator+= (const QByteArray & ba )
QByteArray &	operator+= (char ch )
QByteArray &	operator+= (const char * str )
bool	operator< (const QString & str ) const
bool	operator<= (const QString & str ) const
QByteArray &	operator= (const QByteArray & other )
QByteArray &	operator= (const char * str )
QByteArray &	operator= (QByteArray && other )
bool	operator== (const QString & str ) const
bool	operator> (const QString & str ) const
bool	operator>= (const QString & str ) const
char &	operator[] (qsizetype i )
char	operator[] (qsizetype i ) const

靜態公共成員

QByteArray	fromBase64 (const QByteArray & base64 , QByteArray::Base64Options options = Base64Encoding)
QByteArray::FromBase64Result	fromBase64Encoding (QByteArray && base64 , QByteArray::Base64Options options = Base64Encoding)
QByteArray::FromBase64Result	fromBase64Encoding (const QByteArray & base64 , QByteArray::Base64Options options = Base64Encoding)
QByteArray	fromCFData (CFDataRef data )
QByteArray	fromEcmaUint8Array (emscripten::val uint8array )
QByteArray	fromHex (const QByteArray & hexEncoded )
QByteArray	fromNSData (const NSData * data )
QByteArray	fromPercentEncoding (const QByteArray & input , char percent = '%')
QByteArray	fromRawCFData (CFDataRef data )
QByteArray	fromRawData (const char * data , qsizetype size )
QByteArray	fromRawNSData (const NSData * data )
QByteArray	fromStdString (const std::string & str )
QByteArray	number (int n , int base = 10)
QByteArray	number (uint n , int base = 10)
QByteArray	number (long n , int base = 10)
QByteArray	number (ulong n , int base = 10)
QByteArray	number (qlonglong n , int base = 10)
QByteArray	number (qulonglong n , int base = 10)
QByteArray	number (double n , char format = 'g', int precision = 6)

qsizetype	erase (QByteArray & ba , const T & t )
qsizetype	erase_if (QByteArray & ba , Predicate pred )
quint16	qChecksum (QByteArrayView data , Qt::ChecksumType standard = Qt::ChecksumIso3309)
QByteArray	qCompress (const QByteArray & data , int compressionLevel = -1)
QByteArray	qCompress (const uchar * data , qsizetype nbytes , int compressionLevel = -1)
QByteArray	qUncompress (const QByteArray & data )
QByteArray	qUncompress (const uchar * data , qsizetype nbytes )
int	qsnprintf (char * str , size_t n , const char * fmt , ...)
int	qstrcmp (const char * str1 , const char * str2 )
char *	qstrcpy (char * dst , const char * src )
char *	qstrdup (const char * src )
int	qstricmp (const char * str1 , const char * str2 )
size_t	qstrlen (const char * str )
int	qstrncmp (const char * str1 , const char * str2 , size_t len )
char *	qstrncpy (char * dst , const char * src , size_t len )
int	qstrnicmp (const char * str1 , const char * str2 , size_t len )
size_t	qstrnlen (const char * str , size_t maxlen )
int	qvsnprintf (char * str , size_t n , const char * fmt , va_list ap )
bool	operator!= (const QByteArray & a1 , const QByteArray & a2 )
bool	operator!= (const QByteArray & a1 , const char * a2 )
bool	operator!= (const char * a1 , const QByteArray & a2 )
QByteArray	operator""_ba (const char * str , size_t size )
QByteArray	operator+ (const QByteArray & a1 , const QByteArray & a2 )
QByteArray	operator+ (const QByteArray & a1 , const char * a2 )
QByteArray	operator+ (const QByteArray & a1 , char a2 )
QByteArray	operator+ (const char * a1 , const QByteArray & a2 )
QByteArray	operator+ (char a1 , const QByteArray & a2 )
bool	operator< (const QByteArray & a1 , const QByteArray & a2 )
bool	operator< (const QByteArray & a1 , const char * a2 )
bool	operator< (const char * a1 , const QByteArray & a2 )
QDataStream &	operator<< (QDataStream & out , const QByteArray & ba )
bool	operator<= (const QByteArray & a1 , const QByteArray & a2 )
bool	operator<= (const QByteArray & a1 , const char * a2 )
bool	operator<= (const char * a1 , const QByteArray & a2 )
bool	operator== (const QByteArray & a1 , const QByteArray & a2 )
bool	operator== (const QByteArray & a1 , const char * a2 )
bool	operator== (const char * a1 , const QByteArray & a2 )
bool	operator> (const QByteArray & a1 , const QByteArray & a2 )
bool	operator> (const QByteArray & a1 , const char * a2 )
bool	operator> (const char * a1 , const QByteArray & a2 )
bool	operator>= (const QByteArray & a1 , const QByteArray & a2 )
bool	operator>= (const QByteArray & a1 , const char * a2 )
bool	operator>= (const char * a1 , const QByteArray & a2 )
QDataStream &	operator>> (QDataStream & in , QByteArray & ba )

宏

	QByteArrayLiteral ( ba )
	QT_NO_CAST_FROM_BYTEARRAY

詳細描述

QByteArray 可以被用於存儲原生字節 (包括 \0) 和傳統 8 位以 \0 結尾的字符串。使用 QByteArray 更方便比使用 const char * 。在幕後，它始終確保數據之後緊跟 \0 終止符，並使用隱式共享 (寫入時拷貝) 以縮減內存用量並避免不必要的數據拷貝。

除 QByteArray 外，Qt 還提供 QString 類以存儲字符串數據。對於大多數目的， QString is the class you want to use. It understands its content as Unicode text (encoded using UTF-16) where QByteArray aims to avoid assumptions about the encoding or semantics of the bytes it stores (aside from a few legacy cases where it uses ASCII). Furthermore, QString is used throughout in the Qt API. The two main cases where QByteArray is appropriate are when you need to store raw binary data, and when memory conservation is critical (e.g., with Qt for Embedded Linux).

One way to initialize a QByteArray is simply to pass a const char * 到其構造函數。例如，以下代碼創建包含數據 Hello 大小為 5 的字節數組：

QByteArray ba("Hello");

盡管 size () is 5, the byte array also maintains an extra '\0' byte at the end so that if a function is used that asks for a pointer to the underlying data (e.g. a call to data ()), the data pointed to is guaranteed to be '\0'-terminated.

QByteArray makes a deep copy of the const char * data, so you can modify it later without experiencing side effects. (If, for example for performance reasons, you don't want to take a deep copy of the data, use QByteArray::fromRawData () instead.)

Another approach is to set the size of the array using resize () and to initialize the data byte by byte. QByteArray uses 0-based indexes, just like C++ arrays. To access the byte at a particular index position, you can use operator[](). On non-const byte arrays, operator[]() returns a reference to a byte that can be used on the left side of an assignment. For example:

QByteArray ba;
ba.resize(5);
ba[0] = 0x3c;
ba[1] = 0xb8;
ba[2] = 0x64;
ba[3] = 0x18;
ba[4] = 0xca;

For read-only access, an alternative syntax is to use at ():

for (qsizetype i = 0; i < ba.size(); ++i) {
    if (ba.at(i) >= 'a' && ba.at(i) <= 'f')
        cout << "Found character in range [a-f]" << endl;
}

at () can be faster than operator[](), because it never causes a 深拷貝的齣現。

要每次提取多個字節，使用 first (), last ()，或 sliced ().

A QByteArray can embed '\0' bytes. The size () function always returns the size of the whole array, including embedded '\0' bytes, but excluding the terminating '\0' added by QByteArray. For example:

QByteArray ba1("ca\0r\0t");
ba1.size();                     // Returns 2.
ba1.constData();                // Returns "ca" with terminating \0.
QByteArray ba2("ca\0r\0t", 3);
ba2.size();                     // Returns 3.
ba2.constData();                // Returns "ca\0" with terminating \0.
QByteArray ba3("ca\0r\0t", 4);
ba3.size();                     // Returns 4.
ba3.constData();                // Returns "ca\0r" with terminating \0.
const char cart[] = {'c', 'a', '\0', 'r', '\0', 't'};
QByteArray ba4(QByteArray::fromRawData(cart, 6));
ba4.size();                     // Returns 6.
ba4.constData();                // Returns "ca\0r\0t" without terminating \0.

If you want to obtain the length of the data up to and excluding the first '\0' byte, call qstrlen () on the byte array.

After a call to resize (), newly allocated bytes have undefined values. To set all the bytes to a particular value, call fill ().

To obtain a pointer to the actual bytes, call data () 或 constData (). These functions return a pointer to the beginning of the data. The pointer is guaranteed to remain valid until a non-const function is called on the QByteArray. It is also guaranteed that the data ends with a '\0' byte unless the QByteArray was created from raw data . This '\0' byte is automatically provided by QByteArray and is not counted in size ().

QByteArray provides the following basic functions for modifying the byte data: append (), prepend (), insert (), replace ()，和 remove ()。例如：

QByteArray x("and");
x.prepend("rock ");         // x == "rock and"
x.append(" roll");          // x == "rock and roll"
x.replace(5, 3, "&");       // x == "rock & roll"

In the above example the replace () function's first two arguments are the position from which to start replacing and the number of bytes that should be replaced.

When data-modifying functions increase the size of the array, they may lead to reallocation of memory for the QByteArray object. When this happens, QByteArray expands by more than it immediately needs so as to have space for further expansion without reallocation until the size of the array has greatly increased.

The insert (), remove () and, when replacing a sub-array with one of different size, replace () functions can be slow ( 綫性時間 ) for large arrays, because they require moving many bytes in the array by at least one position in memory.

If you are building a QByteArray gradually and know in advance approximately how many bytes the QByteArray will contain, you can call reserve (), asking QByteArray to preallocate a certain amount of memory. You can also call capacity () to find out how much memory the QByteArray actually has allocated.

Note that using non-const operators and functions can cause QByteArray to do a deep copy of the data, due to 隱式共享 .

QByteArray provides STL 樣式迭代器 ( QByteArray::const_iterator and QByteArray::iterator ). In practice, iterators are handy when working with generic algorithms provided by the C++ standard library.

注意： Iterators and references to individual QByteArray elements are subject to stability issues. They are often invalidated when a QByteArray-modifying operation (e.g. insert () 或 remove ()) is called. When stability and iterator-like functionality is required, you should use indexes instead of iterators as they are not tied to QByteArray's internal state and thus do not get invalidated.

注意： Iterators over a QByteArray, and references to individual bytes within one, cannot be relied on to remain valid when any non-const method of the QByteArray is called. Accessing such an iterator or reference after the call to a non-const method leads to undefined behavior. When stability for iterator-like functionality is required, you should use indexes instead of iterators as they are not tied to QByteArray's internal state and thus do not get invalidated.

If you want to find all occurrences of a particular byte or sequence of bytes in a QByteArray, use indexOf () 或 lastIndexOf (). The former searches forward starting from a given index position, the latter searches backward. Both return the index position of the byte sequence if they find it; otherwise, they return -1. For example, here's a typical loop that finds all occurrences of a particular string:

QByteArray ba("We must be <b>bold</b>, very <b>bold</b>");
qsizetype j = 0;
while ((j = ba.indexOf("<b>", j)) != -1) {
    cout << "Found <b> tag at index position " << j << endl;
    ++j;
}

If you simply want to check whether a QByteArray contains a particular byte sequence, use contains (). If you want to find out how many times a particular byte sequence occurs in the byte array, use count(). If you want to replace all occurrences of a particular value with another, use one of the two-parameter replace () overloads.

QByteArray s can be compared using overloaded operators such as operator<(), operator<=(), operator==(), operator>=(), and so on. The comparison is based exclusively on the numeric values of the bytes and is very fast, but is not what a human would expect. QString::localeAwareCompare () is a better choice for sorting user-interface strings.

For historical reasons, QByteArray distinguishes between a null byte array and an empty byte array. A null byte array is a byte array that is initialized using QByteArray's default constructor or by passing (const char *)0 to the constructor. An empty byte array is any byte array with size 0. A null byte array is always empty, but an empty byte array isn't necessarily null:

QByteArray().isNull();          // returns true
QByteArray().isEmpty();         // returns true
QByteArray("").isNull();        // returns false
QByteArray("").isEmpty();       // returns true
QByteArray("abc").isNull();     // returns false
QByteArray("abc").isEmpty();    // returns false

所有函數除瞭 isNull () treat null byte arrays the same as empty byte arrays. For example, data () returns a valid pointer ( not nullptr) to a '\0' byte for a null byte array and QByteArray() compares equal to QByteArray(""). We recommend that you always use isEmpty () and avoid isNull ().

最大尺寸和內存不足情況

The maximum size of QByteArray depends on the architecture. Most 64-bit systems can allocate more than 2 GB of memory, with a typical limit of 2^63 bytes. The actual value also depends on the overhead required for managing the data block. As a result, you can expect the maximum size of 2 GB minus overhead on 32-bit platforms, and 2^63 bytes minus overhead on 64-bit platforms. The number of elements that can be stored in a QByteArray is this maximum size.

When memory allocation fails, QByteArray throws a std::bad_alloc exception if the application is being compiled with exception support. Out of memory conditions in Qt containers are the only case where Qt will throw exceptions. If exceptions are disabled, then running out of memory is undefined behavior.

Note that the operating system may impose further limits on applications holding a lot of allocated memory, especially large, contiguous blocks. Such considerations, the configuration of such behavior or any mitigation are outside the scope of the QByteArray API.

C locale and ASCII functions

QByteArray generally handles data as bytes, without presuming any semantics; where it does presume semantics, it uses the C locale and ASCII encoding. Standard Unicode encodings are supported by QString , other encodings may be supported using QStringEncoder and QStringDecoder to convert to Unicode. For locale-specific interpretation of text, use QLocale or QString .

C Strings

Traditional C strings, also known as '\0'-terminated strings, are sequences of bytes, specified by a start-point and implicitly including each byte up to, but not including, the first '\0' byte thereafter. Methods that accept such a pointer, without a length, will interpret it as this sequence of bytes. Such a sequence, by construction, cannot contain a '\0' byte.

Other overloads accept a start-pointer and a byte-count; these use the given number of bytes, following the start address, regardless of whether any of them happen to be '\0' bytes. In some cases, where there is no overload taking only a pointer, passing a length of -1 will cause the method to use the offset of the first '\0' byte after the pointer as the length; a length of -1 should only be passed if the method explicitly says it does this (in which case it is typically a default argument).

Spacing Characters

A frequent requirement is to remove spacing characters from a byte array ( '\n' , '\t' , ' ' , etc.). If you want to remove spacing from both ends of a QByteArray, use trimmed (). If you want to also replace each run of spacing characters with a single space character within the byte array, use simplified (). Only ASCII spacing characters are recognized for these purposes.

數字字符串轉換

Functions that perform conversions between numeric data types and string representations are performed in the C locale, regardless of the user's locale settings. Use QLocale to perform locale-aware conversions between numbers and strings.

Character Case

In QByteArray, the notion of uppercase and lowercase and of case-independent comparison is limited to ASCII. Non-ASCII characters are treated as caseless, since their case depends on encoding. This affects functions that support a case insensitive option or that change the case of their arguments. Functions that this affects include compare (), isLower (), isUpper (), toLower () 和 toUpper ().

This issue does not apply to QString s since they represent characters using Unicode.

另請參閱 QByteArrayView , QString ，和 QBitArray .

成員類型文檔編製

enum QByteArray:: Base64Option
flags QByteArray:: Base64Options

This enum contains the options available for encoding and decoding Base64. Base64 is defined by RFC 4648 , with the following options:

常量	值	描述
`QByteArray::Base64Encoding`	`0`	(default) The regular Base64 alphabet, called simply "base64"
`QByteArray::Base64UrlEncoding`	`1`	An alternate alphabet, called "base64url", which replaces two characters in the alphabet to be more friendly to URLs.
`QByteArray::KeepTrailingEquals`	`0`	(default) Keeps the trailing padding equal signs at the end of the encoded data, so the data is always a size multiple of four.
`QByteArray::OmitTrailingEquals`	`2`	Omits adding the padding equal signs at the end of the encoded data.
`QByteArray::IgnoreBase64DecodingErrors`	`0`	When decoding Base64-encoded data, ignores errors in the input; invalid characters are simply skipped. This enum value has been added in Qt 5.15.
`QByteArray::AbortOnBase64DecodingErrors`	`4`	When decoding Base64-encoded data, stops at the first decoding error. This enum value has been added in Qt 5.15.

QByteArray::fromBase64Encoding () 和 QByteArray::fromBase64 () ignore the KeepTrailingEquals and OmitTrailingEquals options. If the IgnoreBase64DecodingErrors option is specified, they will not flag errors in case trailing equal signs are missing or if there are too many of them. If instead the AbortOnBase64DecodingErrors is specified, then the input must either have no padding or have the correct amount of equal signs.

The Base64Options type is a typedef for QFlags <Base64Option>. It stores an OR combination of Base64Option values.

QByteArray:: const_iterator

此 typedef 提供 STL 樣式 const 迭代器為 QByteArray .

另請參閱 QByteArray::const_reverse_iterator and QByteArray::iterator .

QByteArray:: const_reverse_iterator

This typedef provides an STL-style const reverse iterator for QByteArray .

另請參閱 QByteArray::reverse_iterator and QByteArray::const_iterator .

QByteArray:: iterator

This typedef provides an STL-style non-const iterator for QByteArray .

另請參閱 QByteArray::reverse_iterator and QByteArray::const_iterator .

QByteArray:: reverse_iterator

This typedef provides an STL-style non-const reverse iterator for QByteArray .

另請參閱 QByteArray::const_reverse_iterator and QByteArray::iterator .

成員函數文檔編製

const char QByteArray:: operator const char () const

const void QByteArray:: operator const void () const

注意： 使用 constData () instead in new code.

Returns a pointer to the data stored in the byte array. The pointer can be used to access the bytes that compose the array. The data is '\0'-terminated.

The pointer remains valid as long as no detach happens and the QByteArray is not modified. This operator is mostly useful to pass a byte array to a function that accepts a const char * .

可以禁用此運算符通過定義 QT_NO_CAST_FROM_BYTEARRAY 當編譯應用程序時。

注意： QByteArray 可以存儲任何字節值 (包括 \0)，但大多數函數需要 char * 自變量，假定數據在遇到首個 \0 時結束。

另請參閱 constData ().

`[static]` QByteArray::FromBase64Result QByteArray:: fromBase64Encoding ( QByteArray && base64 , QByteArray::Base64Options options = Base64Encoding)

`[static]` QByteArray::FromBase64Result QByteArray:: fromBase64Encoding (const QByteArray & base64 , QByteArray::Base64Options options = Base64Encoding)

這是重載函數。

Decodes the Base64 array base64 , using the options defined by options 。若 options 包含 IgnoreBase64DecodingErrors (the default), the input is not checked for validity; invalid characters in the input are skipped, enabling the decoding process to continue with subsequent characters. If options 包含 AbortOnBase64DecodingErrors , then decoding will stop at the first invalid character.

例如：

void process(const QByteArray &);
if (auto result = QByteArray::fromBase64Encoding(encodedData))
    process(*result);

The algorithm used to decode Base64-encoded data is defined in RFC 4648 .

Returns a QByteArrayFromBase64Result object, containing the decoded data and a flag telling whether decoding was successful. If the AbortOnBase64DecodingErrors option was passed and the input data was invalid, it is unspecified what the decoded data contains.

另請參閱 toBase64 ().

`[constexpr]` QByteArray:: QByteArray ()

構造空字節數組。

另請參閱 isEmpty ().

QByteArray:: QByteArray (const char * data , qsizetype size = -1)

構造字節數組包含前 size 字節的數組 data .

若 data 為 0，構造 null 字節數組。

若 size 為負， data is assumed to point to a '\0'-terminated string and its length is determined dynamically.

QByteArray 製作字符串數據的深拷貝。

另請參閱 fromRawData ().

QByteArray:: QByteArray ( qsizetype size , char ch )

構造字節數組大小為 size with every byte set to ch .

另請參閱 fill ().

QByteArray:: QByteArray ( qsizetype size , Qt::Initialization )

構造字節數組大小為 size with uninitialized contents.

QByteArray:: QByteArray (const QByteArray & other )

構造副本為 other .

此操作花費常量時間，因為 QByteArray 隱式共享 . This makes returning a QByteArray from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), taking 綫性時間 .

另請參閱 operator= ().

QByteArray:: QByteArray ( QByteArray && other )

移動構造 QByteArray 實例，使之指嚮同一對象如 other 所指嚮的。

QByteArray:: ~QByteArray ()

銷毀字節數組。

QByteArray &QByteArray:: append (const QByteArray & ba )

追加字節數組 ba 到此字節數組的末尾。

範例：

QByteArray x("free");
QByteArray y("dom");
x.append(y);
// x == "freedom"

這如同 insert( size (), ba ).

注意： QByteArray 是隱式共享類。因此，若追加到空字節數組，那麼字節數組將僅僅共享的數據保持在 ba 。在這種情況下，不進行數據拷貝，花費常量時間。若共享實例被修改，它將被拷貝 (寫時拷貝)，花費綫性時間 .

若要追加到的字節數組非空，履行數據深拷貝，花費綫性時間 .

append() 函數通常非常快 ( 常量時間 )，因為 QByteArray preallocates extra space at the end of the data, so it can grow without reallocating the entire array each time.

另請參閱 operator+= (), prepend ()，和 insert ().

QByteArray &QByteArray:: append ( char ch )

這是重載函數。

Appends the byte ch 到此字節數組。

QByteArray &QByteArray:: append ( qsizetype count , char ch )

這是重載函數。

追加 count copies of byte ch 到此字節數組，並返迴此字節數組的引用。

若 count 為負 (或 0)，什麼都不會追加到字節數組。

QByteArray &QByteArray:: append (const char * str )

這是重載函數。

Appends the '\0'-terminated string str 到此字節數組。

QByteArray &QByteArray:: append (const char * str , qsizetype len )

這是重載函數。

追加第一 len bytes starting at str to this byte array and returns a reference to this byte array. The bytes appended may include '\0' bytes.

若 len 為負， str will be assumed to be a '\0'-terminated string and the length to be copied will be determined automatically using qstrlen ().

若 len 為 0 或 str is null, nothing is appended to the byte array. Ensure that len is not longer than str .

QByteArray &QByteArray:: append ( QByteArrayView data )

這是重載函數。

追加 data 到此字節數組。

char QByteArray:: at ( qsizetype i ) const

返迴字節按索引位置 i 在字節數組中。

i 必須是字節數組中的有效索引位置 (即 0 <= i < size ()).

另請參閱 operator[] ().

char QByteArray:: back () const

Returns the last byte in the byte array. Same as at(size() - 1) .

此函數為兼容 STL (標準模闆庫) 提供。

警告： 空字節數組調用此函數，會構成未定義行為。

另請參閱 front (), at ()，和 operator[] ().

char &QByteArray:: back ()

Returns a reference to the last byte in the byte array. Same as operator[](size() - 1) .

此函數為兼容 STL (標準模闆庫) 提供。

警告： 空字節數組調用此函數，會構成未定義行為。

另請參閱 front (), at ()，和 operator[] ().

QByteArray::iterator QByteArray:: begin ()

返迴 STL 樣式迭代器 pointing to the first byte in the byte-array.

警告： The returned iterator is invalidated on detachment or when the QByteArray 被修改。

另請參閱 constBegin () 和 end ().

QByteArray::const_iterator QByteArray:: begin () const

此函數重載 begin()。

qsizetype QByteArray:: capacity () const

Returns the maximum number of bytes that can be stored in the byte array without forcing a reallocation.

The sole purpose of this function is to provide a means of fine tuning QByteArray 's memory usage. In general, you will rarely ever need to call this function. If you want to know how many bytes are in the byte array, call size ().

注意： a statically allocated byte array will report a capacity of 0, even if it's not empty.

注意： The free space position in the allocated memory block is undefined. In other words, one should not assume that the free memory is always located after the initialized elements.

另請參閱 reserve () 和 squeeze ().

QByteArray::const_iterator QByteArray:: cbegin () const

返迴常量 STL 樣式迭代器 pointing to the first byte in the byte-array.

警告： The returned iterator is invalidated on detachment or when the QByteArray 被修改。

另請參閱 begin () 和 cend ().

QByteArray::const_iterator QByteArray:: cend () const

返迴常量 STL 樣式迭代器 pointing just after the last byte in the byte-array.

警告： The returned iterator is invalidated on detachment or when the QByteArray 被修改。

另請參閱 cbegin () 和 end ().

void QByteArray:: chop ( qsizetype n )

移除 n bytes from the end of the byte array.

若 n 大於 size (), the result is an empty byte array.

範例：

QByteArray ba("STARTTLS\r\n");
ba.chop(2);                 // ba == "STARTTLS"

另請參閱 truncate (), resize ()，和 first ().

QByteArray QByteArray:: chopped ( qsizetype len ) const

返迴的字節數組包含最左 size () - len 字節對於此字節數組。

注意： 行為未定義若 len 為負或大於 size ().

另請參閱 endsWith (), first (), last (), sliced (), chop ()，和 truncate ().

void QByteArray:: clear ()

Clears the contents of the byte array and makes it null.

另請參閱 resize () 和 isNull ().

`[since 6.0]` int QByteArray:: compare ( QByteArrayView bv , Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns an integer less than, equal to, or greater than zero depending on whether this QByteArray sorts before, at the same position as, or after the QByteArrayView bv . The comparison is performed according to case sensitivity cs .

該函數在 Qt 6.0 引入。

另請參閱 operator== and Character Case .

QByteArray::const_iterator QByteArray:: constBegin () const

返迴常量 STL 樣式迭代器 pointing to the first byte in the byte-array.

警告： The returned iterator is invalidated on detachment or when the QByteArray 被修改。

另請參閱 begin () 和 constEnd ().

const char *QByteArray:: constData () const

Returns a pointer to the const data stored in the byte array. The pointer can be used to access the bytes that compose the array. The data is '\0'-terminated unless the QByteArray object was created from raw data.

The pointer remains valid as long as no detach happens and the QByteArray is not modified.

此函數主要用於將字節數組傳遞給的函數接受 const char * .

注意： QByteArray 可以存儲任何字節值 (包括 \0)，但大多數函數需要 char * 自變量，假定數據在遇到首個 \0 時結束。

另請參閱 data (), operator[] ()，和 fromRawData ().

QByteArray::const_iterator QByteArray:: constEnd () const

返迴常量 STL 樣式迭代器 pointing just after the last byte in the byte-array.

警告： The returned iterator is invalidated on detachment or when the QByteArray 被修改。

另請參閱 constBegin () 和 end ().

`[since 6.0]` bool QByteArray:: contains ( QByteArrayView bv ) const

返迴 true if this byte array contains an occurrence of the sequence of bytes viewed by bv ；否則返迴 false .

該函數在 Qt 6.0 引入。

另請參閱 indexOf () 和 count ().

bool QByteArray:: contains ( char ch ) const

這是重載函數。

返迴 true if the byte array contains the byte ch ；否則返迴 false .

`[since 6.0]` qsizetype QByteArray:: count ( QByteArrayView bv ) const

Returns the number of (potentially overlapping) occurrences of the sequence of bytes viewed by bv in this byte array.

該函數在 Qt 6.0 引入。

另請參閱 contains () 和 indexOf ().

qsizetype QByteArray:: count ( char ch ) const

這是重載函數。

Returns the number of occurrences of byte ch 在字節數組中。

另請參閱 contains () 和 indexOf ().

QByteArray::const_reverse_iterator QByteArray:: crbegin () const

返迴常量 STL-style reverse iterator pointing to the first byte in the byte-array, in reverse order.

警告： The returned iterator is invalidated on detachment or when the QByteArray 被修改。

另請參閱 begin (), rbegin ()，和 rend ().

QByteArray::const_reverse_iterator QByteArray:: crend () const

返迴常量 STL-style reverse iterator pointing just after the last byte in the byte-array, in reverse order.

警告： The returned iterator is invalidated on detachment or when the QByteArray 被修改。

另請參閱 end (), rend ()，和 rbegin ().

char *QByteArray:: data ()

Returns a pointer to the data stored in the byte array. The pointer can be used to access and modify the bytes that compose the array. The data is '\0'-terminated, i.e. the number of bytes you can access following the returned pointer is size () + 1, including the '\0' terminator.

範例：

QByteArray ba("Hello world");
char *data = ba.data();
while (*data) {
    cout << "[" << *data << "]" << endl;
    ++data;
}

The pointer remains valid as long as no detach happens and the QByteArray is not modified.

For read-only access, constData () 更快，因為它從不導緻深拷貝的齣現。

此函數主要用於將字節數組傳遞給的函數接受 const char * .

以下範例製作由 data() 返迴的 char* 副本，但會破壞堆並導緻崩潰，因為它沒有為末尾 \0 分配字節：

QString tmp = "test";
QByteArray text = tmp.toLocal8Bit();
char *data = new char[text.size()];
strcpy(data, text.data());
delete [] data;

這個分配瞭正確的空間數量：

QString tmp = "test";
QByteArray text = tmp.toLocal8Bit();
char *data = new char[text.size() + 1];
strcpy(data, text.data());
delete [] data;

注意： QByteArray 可以存儲任何字節值 (包括 \0)，但大多數函數需要 char * 自變量，假定數據在遇到首個 \0 時結束。

另請參閱 constData () 和 operator[] ().

const char *QByteArray:: data () const

這是重載函數。

QByteArray::iterator QByteArray:: end ()

返迴 STL 樣式迭代器 pointing just after the last byte in the byte-array.

警告： The returned iterator is invalidated on detachment or when the QByteArray 被修改。

另請參閱 begin () 和 constEnd ().

QByteArray::const_iterator QByteArray:: end () const

此函數重載 end()。

`[since 6.0]` bool QByteArray:: endsWith ( QByteArrayView bv ) const

返迴 true if this byte array ends with the sequence of bytes viewed by bv ；否則返迴 false .

範例：

QByteArray url("http://qt-project.org/doc/qt-5.0/qtdoc/index.html");
if (url.endsWith(".html"))
    ...

該函數在 Qt 6.0 引入。

另請參閱 startsWith () 和 last ().

bool QByteArray:: endsWith ( char ch ) const

這是重載函數。

返迴 true if this byte array ends with byte ch ；否則返迴 false .

`[since 6.1]` QByteArray::iterator QByteArray:: erase ( QByteArray::const_iterator first , QByteArray::const_iterator last )

Removes from the byte array the characters in the half-open range [ first , last ). Returns an iterator to the character referred to by last before the erase.

This function was introduced in Qt 6.1.

`[since 6.5]` QByteArray::iterator QByteArray:: erase ( QByteArray::const_iterator it )

Removes the character denoted by it from the byte array. Returns an iterator to the character immediately after the erased character.

QByteArray ba = "abcdefg";
auto it = ba.erase(ba.cbegin()); // ba is now "bcdefg" and it points to "b"

This function was introduced in Qt 6.5.

QByteArray &QByteArray:: fill ( char ch , qsizetype size = -1)

Sets every byte in the byte array to ch 。若 size is different from -1 (the default), the byte array is resized to size size 事先。

範例：

QByteArray ba("Istambul");
ba.fill('o');
// ba == "oooooooo"
ba.fill('X', 2);
// ba == "XX"

另請參閱 resize ().

`[since 6.0]` QByteArray QByteArray:: first ( qsizetype n ) const

返迴第一 n bytes of the byte array.

注意： 行為未定義當 n < 0 or n > size ().

範例：

QByteArray x("Pineapple");
QByteArray y = x.first(4);
// y == "Pine"

該函數在 Qt 6.0 引入。

另請參閱 last (), sliced (), startsWith (), chopped (), chop ()，和 truncate ().

`[static]` QByteArray QByteArray:: fromBase64 (const QByteArray & base64 , QByteArray::Base64Options options = Base64Encoding)

Returns a decoded copy of the Base64 array base64 , using the options defined by options 。若 options 包含 IgnoreBase64DecodingErrors (the default), the input is not checked for validity; invalid characters in the input are skipped, enabling the decoding process to continue with subsequent characters. If options 包含 AbortOnBase64DecodingErrors , then decoding will stop at the first invalid character.

例如：

QByteArray text = QByteArray::fromBase64("UXQgaXMgZ3JlYXQh");
text.data();            // returns "Qt is great!"
QByteArray::fromBase64("PHA+SGVsbG8/PC9wPg==", QByteArray::Base64Encoding); // returns "<p>Hello?</p>"
QByteArray::fromBase64("PHA-SGVsbG8_PC9wPg==", QByteArray::Base64UrlEncoding); // returns "<p>Hello?</p>"

The algorithm used to decode Base64-encoded data is defined in RFC 4648 .

Returns the decoded data, or, if the AbortOnBase64DecodingErrors option was passed and the input data was invalid, an empty byte array.

注意： The fromBase64Encoding () function is recommended in new code.

另請參閱 toBase64 () 和 fromBase64Encoding ().

`[static]` QByteArray QByteArray:: fromCFData ( CFDataRef data )

構造新的 QByteArray containing a copy of the CFData data .

另請參閱 fromRawCFData (), fromRawData (), toRawCFData ()，和 toCFData ().

`[static, since 6.5]` QByteArray QByteArray:: fromEcmaUint8Array ( emscripten::val uint8array )

構造新的 QByteArray containing a copy of the Uint8Array uint8array .

This function transfers data from a JavaScript data buffer - which is not addressable from C++ code - to heap memory owned by a QByteArray . The Uint8Array can be released once this function returns and a copy has been made.

The uint8array argument must an emscripten::val referencing an Uint8Array object, e.g. obtained from a global JavaScript variable:

emscripten::val uint8array = emscripten::val::global("g_uint8array");
QByteArray byteArray = QByteArray::fromEcmaUint8Array(uint8array);

This function returns a null QByteArray if the size of the Uint8Array exceeds the maximum capacity of QByteArray , or if the uint8array argument is not of the Uint8Array type.

This function was introduced in Qt 6.5.

另請參閱 toEcmaUint8Array ().

`[static]` QByteArray QByteArray:: fromHex (const QByteArray & hexEncoded )

Returns a decoded copy of the hex encoded array hexEncoded . Input is not checked for validity; invalid characters in the input are skipped, enabling the decoding process to continue with subsequent characters.

例如：

QByteArray text = QByteArray::fromHex("517420697320677265617421");
text.data();            // returns "Qt is great!"

另請參閱 toHex ().

`[static]` QByteArray QByteArray:: fromNSData (const NSData * data )

構造新的 QByteArray containing a copy of the NSData data .

另請參閱 fromRawNSData (), fromRawData (), toNSData ()，和 toRawNSData ().

`[static]` QByteArray QByteArray:: fromPercentEncoding (const QByteArray & input , char percent = '%')

Decodes input from URI/URL-style percent-encoding.

Returns a byte array containing the decoded text. The percent parameter allows use of a different character than '%' (for instance, '_' or '=') as the escape character. Equivalent to input. percentDecoded (percent).

例如：

QByteArray text = QByteArray::fromPercentEncoding("Qt%20is%20great%33");
qDebug("%s", text.data());      // reports "Qt is great!"

另請參閱 percentDecoded ().

`[static]` QByteArray QByteArray:: fromRawCFData ( CFDataRef data )

構造 QByteArray that uses the bytes of the CFData data .

The data 的字節不拷貝。

The caller guarantees that the CFData will not be deleted or modified as long as this QByteArray object exists.

另請參閱 fromCFData (), fromRawData (), toRawCFData ()，和 toCFData ().

`[static]` QByteArray QByteArray:: fromRawData (const char * data , qsizetype size )

構造 QByteArray that uses the first size bytes of the data array. The bytes are not copied. The QByteArray will contain the data pointer. The caller guarantees that data will not be deleted or modified as long as this QByteArray and any copies of it exist that have not been modified. In other words, because QByteArray 是隱式共享 class and the instance returned by this function contains the data pointer, the caller must not delete data or modify it directly as long as the returned QByteArray and any copies exist. However, QByteArray 未擁有所有權對於 data , so the QByteArray destructor will never delete the raw data , even when the last QByteArray referring to data 被銷毀。

A subsequent attempt to modify the contents of the returned QByteArray or any copy made from it will cause it to create a deep copy of the data array before doing the modification. This ensures that the raw data array itself will never be modified by QByteArray .

Here is an example of how to read data using a QDataStream on raw data in memory without copying the raw data into a QByteArray :

 static const char mydata[] = {
    '\x00', '\x00', '\x03', '\x84', '\x78', '\x9c', '\x3b', '\x76',
    '\xec', '\x18', '\xc3', '\x31', '\x0a', '\xf1', '\xcc', '\x99',
    ...
    '\x6d', '\x5b'
};
QByteArray data = QByteArray::fromRawData(mydata, sizeof(mydata));
QDataStream in(&data, QIODevice::ReadOnly);
...

警告： A byte array created with fromRawData() is not '\0'-terminated, unless the raw data contains a '\0' byte at position size . While that does not matter for QDataStream or functions like indexOf (), passing the byte array to a function accepting a const char * expected to be '\0'-terminated will fail.

另請參閱 setRawData (), data ()，和 constData ().

`[static]` QByteArray QByteArray:: fromRawNSData (const NSData * data )

構造 QByteArray that uses the bytes of the NSData data .

The data 的字節不拷貝。

The caller guarantees that the NSData will not be deleted or modified as long as this QByteArray object exists.

另請參閱 fromNSData (), fromRawData (), toRawNSData ()，和 toNSData ().

`[static]` QByteArray QByteArray:: fromStdString (const std::string & str )

返迴副本為 str string as a QByteArray .

另請參閱 toStdString () 和 QString::fromStdString ().

char QByteArray:: front () const

Returns the first byte in the byte array. Same as at(0) .

此函數為兼容 STL (標準模闆庫) 提供。

警告： 空字節數組調用此函數，會構成未定義行為。

另請參閱 back (), at ()，和 operator[] ().

char &QByteArray:: front ()

Returns a reference to the first byte in the byte array. Same as operator[](0) .

此函數為兼容 STL (標準模闆庫) 提供。

警告： 空字節數組調用此函數，會構成未定義行為。

另請參閱 back (), at ()，和 operator[] ().

`[since 6.0]` qsizetype QByteArray:: indexOf ( QByteArrayView bv , qsizetype from = 0) const

Returns the index position of the start of the first occurrence of the sequence of bytes viewed by bv in this byte array, searching forward from index position from . Returns -1 if no match is found.

範例：

QByteArray x("sticky question");
QByteArrayView y("sti");
x.indexOf(y);               // returns 0
x.indexOf(y, 1);            // returns 10
x.indexOf(y, 10);           // returns 10
x.indexOf(y, 11);           // returns -1

該函數在 Qt 6.0 引入。

另請參閱 lastIndexOf (), contains ()，和 count ().

qsizetype QByteArray:: indexOf ( char ch , qsizetype from = 0) const

這是重載函數。

Returns the index position of the start of the first occurrence of the byte ch in this byte array, searching forward from index position from . Returns -1 if no match is found.

範例：

QByteArray ba("ABCBA");
ba.indexOf("B");            // returns 1
ba.indexOf("B", 1);         // returns 1
ba.indexOf("B", 2);         // returns 3
ba.indexOf("X");            // returns -1

另請參閱 lastIndexOf () 和 contains ().

`[since 6.0]` QByteArray &QByteArray:: insert ( qsizetype i , QByteArrayView data )

插入 data at index position i and returns a reference to this byte array.

範例：

QByteArray ba("Meal");
ba.insert(1, QByteArrayView("ontr"));
// ba == "Montreal"

For large byte arrays, this operation can be slow ( 綫性時間 ), because it requires moving all the bytes at indexes i and above by at least one position further in memory.

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i .

該函數在 Qt 6.0 引入。

另請參閱 append (), prepend (), replace ()，和 remove ().

QByteArray &QByteArray:: insert ( qsizetype i , const char * s )

插入 s at index position i and returns a reference to this byte array.

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i .

The function is equivalent to insert(i, QByteArrayView(s))

另請參閱 append (), prepend (), replace ()，和 remove ().

QByteArray &QByteArray:: insert ( qsizetype i , const QByteArray & data )

插入 data at index position i and returns a reference to this byte array.

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i .

另請參閱 append (), prepend (), replace ()，和 remove ().

QByteArray &QByteArray:: insert ( qsizetype i , qsizetype count , char ch )

這是重載函數。

插入 count copies of byte ch at index position i 在字節數組中。

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i .

QByteArray &QByteArray:: insert ( qsizetype i , char ch )

這是重載函數。

Inserts byte ch at index position i 在字節數組中。

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i .

QByteArray &QByteArray:: insert ( qsizetype i , const char * data , qsizetype len )

這是重載函數。

插入 len bytes, starting at data , at position i 在字節數組中。

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i .

bool QByteArray:: isEmpty () const

返迴 true if the byte array has size 0; otherwise returns false .

範例：

QByteArray().isEmpty();         // returns true
QByteArray("").isEmpty();       // returns true
QByteArray("abc").isEmpty();    // returns false

另請參閱 size ().

bool QByteArray:: isLower () const

返迴 true if this byte array is lowercase, that is, if it's identical to its toLower () folding.

Note that this does not mean that the byte array only contains lowercase letters; only that it contains no ASCII uppercase letters.

另請參閱 isUpper () 和 toLower ().

bool QByteArray:: isNull () const

返迴 true if this byte array is null; otherwise returns false .

範例：

QByteArray().isNull();          // returns true
QByteArray("").isNull();        // returns false
QByteArray("abc").isNull();     // returns false

Qt makes a distinction between null byte arrays and empty byte arrays for historical reasons. For most applications, what matters is whether or not a byte array contains any data, and this can be determined using isEmpty ().

另請參閱 isEmpty ().

bool QByteArray:: isUpper () const

返迴 true if this byte array is uppercase, that is, if it's identical to its toUpper () folding.

Note that this does not mean that the byte array only contains uppercase letters; only that it contains no ASCII lowercase letters.

另請參閱 isLower () 和 toUpper ().

`[since 6.3]` bool QByteArray:: isValidUtf8 () const

返迴 true if this byte array contains valid UTF-8 encoded data, or false 否則。

This function was introduced in Qt 6.3.

`[since 6.0]` QByteArray QByteArray:: last ( qsizetype n ) const

Returns the last n bytes of the byte array.

注意： 行為未定義當 n < 0 or n > size ().

範例：

QByteArray x("Pineapple");
QByteArray y = x.last(5);
// y == "apple"

該函數在 Qt 6.0 引入。

另請參閱 first (), sliced (), endsWith (), chopped (), chop ()，和 truncate ().

`[since 6.0]` qsizetype QByteArray:: lastIndexOf ( QByteArrayView bv , qsizetype from ) const

Returns the index position of the start of the last occurrence of the sequence of bytes viewed by bv in this byte array, searching backward from index position from .

若 from is -1, the search starts at the last character; if it is -2, at the next to last character and so on.

Returns -1 if no match is found.

範例：

QByteArray x("crazy azimuths");
QByteArrayView y("az");
x.lastIndexOf(y);           // returns 6
x.lastIndexOf(y, 6);        // returns 6
x.lastIndexOf(y, 5);        // returns 2
x.lastIndexOf(y, 1);        // returns -1

注意： When searching for a 0-length bv , the match at the end of the data is excluded from the search by a negative from , even though -1 is normally thought of as searching from the end of the byte array: the match at the end is after the last character, so it is excluded. To include such a final empty match, either give a positive value for from or omit the from parameter entirely.

該函數在 Qt 6.0 引入。

另請參閱 indexOf (), contains ()，和 count ().

qsizetype QByteArray:: lastIndexOf ( char ch , qsizetype from = -1) const

這是重載函數。

Returns the index position of the start of the last occurrence of byte ch in this byte array, searching backward from index position from 。若 from is -1 (the default), the search starts at the last byte (at index size () - 1). Returns -1 if no match is found.

範例：

QByteArray ba("ABCBA");
ba.lastIndexOf("B");        // returns 3
ba.lastIndexOf("B", 3);     // returns 3
ba.lastIndexOf("B", 2);     // returns 1
ba.lastIndexOf("X");        // returns -1

另請參閱 indexOf () 和 contains ().

`[since 6.2]` qsizetype QByteArray:: lastIndexOf ( QByteArrayView bv ) const

這是重載函數。

Returns the index position of the start of the last occurrence of the sequence of bytes viewed by bv in this byte array, searching backward from the end of the byte array. Returns -1 if no match is found.

範例：

QByteArray x("crazy azimuths");
QByteArrayView y("az");
x.lastIndexOf(y);           // returns 6
x.lastIndexOf(y, 6);        // returns 6
x.lastIndexOf(y, 5);        // returns 2
x.lastIndexOf(y, 1);        // returns -1

This function was introduced in Qt 6.2.

另請參閱 indexOf (), contains ()，和 count ().

QByteArray QByteArray:: left ( qsizetype len ) const

Returns a byte array that contains the first len 字節對於此字節數組。

If you know that len cannot be out of bounds, use first () instead in new code, because it is faster.

返迴整個字節數組若 len 大於 size ().

返迴空 QByteArray if len is smaller than 0.

另請參閱 first (), last (), startsWith (), chopped (), chop ()，和 truncate ().

QByteArray QByteArray:: leftJustified ( qsizetype width , char fill = ' ', bool truncate = false) const

Returns a byte array of size width that contains this byte array padded with the fill byte.

若 truncate is false and the size () of the byte array is more than width , then the returned byte array is a copy of this byte array.

若 truncate is true and the size () of the byte array is more than width , then any bytes in a copy of the byte array after position width are removed, and the copy is returned.

範例：

QByteArray x("apple");
QByteArray y = x.leftJustified(8, '.');   // y == "apple..."

另請參閱 rightJustified ().

qsizetype QByteArray:: length () const

如同 size ().

QByteArray QByteArray:: mid ( qsizetype pos , qsizetype len = -1) const

返迴的字節數組包含 len 字節從此字節數組，起始於位置 pos .

If you know that pos and len cannot be out of bounds, use sliced () instead in new code, because it is faster.

若 len 為 -1 (默認)，或 pos + len >= size (), returns a byte array containing all bytes starting at position pos until the end of the byte array.

另請參閱 first (), last (), sliced (), chopped (), chop ()，和 truncate ().

`[static]` QByteArray QByteArray:: number ( int n , int base = 10)

Returns a byte-array representing the whole number n as text.

Returns a byte array containing a string representing n ，使用指定 base (ten by default). Bases 2 through 36 are supported, using letters for digits beyond 9: A is ten, B is eleven and so on.

範例：

int n = 63;
QByteArray::number(n);              // returns "63"
QByteArray::number(n, 16);          // returns "3f"
QByteArray::number(n, 16).toUpper();  // returns "3F"

注意： The format of the number is not localized; the default C locale is used regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

另請參閱 setNum () 和 toInt ().

`[static]` QByteArray QByteArray:: number ( uint n , int base = 10)

這是重載函數。

另請參閱 toUInt ().

`[static]` QByteArray QByteArray:: number ( long n , int base = 10)

這是重載函數。

另請參閱 toLong ().

`[static]` QByteArray QByteArray:: number ( ulong n , int base = 10)

這是重載函數。

另請參閱 toULong ().

`[static]` QByteArray QByteArray:: number ( qlonglong n , int base = 10)

這是重載函數。

另請參閱 toLongLong ().

`[static]` QByteArray QByteArray:: number ( qulonglong n , int base = 10)

這是重載函數。

另請參閱 toULongLong ().

`[static]` QByteArray QByteArray:: number ( double n , char format = 'g', int precision = 6)

這是重載函數。

Returns a byte-array representing the floating-point number n as text.

Returns a byte array containing a string representing n , with a given format and precision , with the same meanings as for QString::number (double, char, int). For example:

QByteArray ba = QByteArray::number(12.3456, 'E', 3);
// ba == 1.235E+01

另請參閱 toDouble () 和 QLocale::FloatingPointPrecisionOption .

`[since 6.4]` QByteArray QByteArray:: percentDecoded ( char percent = '%') const

Decodes URI/URL-style percent-encoding.

Returns a byte array containing the decoded text. The percent parameter allows use of a different character than '%' (for instance, '_' or '=') as the escape character.

例如：

QByteArray encoded("Qt%20is%20great%33");
QByteArray decoded = encoded.percentDecoded(); // Set to "Qt is great!"

注意： 給定無效輸入 (譬如：包含 %G5 序列的字符串，不是有效十六進製數字)，輸齣也將無效。例如：%G5 序列可以解碼為 W。

This function was introduced in Qt 6.4.

另請參閱 toPercentEncoding () 和 QUrl::fromPercentEncoding ().

QByteArray &QByteArray:: prepend ( QByteArrayView ba )

Prepends the byte array view ba 到此字節數組，並返迴此字節數組的引用。

This operation is typically very fast ( 常量時間 )，因為 QByteArray preallocates extra space at the beginning of the data, so it can grow without reallocating the entire array each time.

範例：

QByteArray x("ship");
QByteArray y("air");
x.prepend(y);
// x == "airship"

這如同 insert(0, ba ).

另請參閱 append () 和 insert ().

QByteArray &QByteArray:: prepend ( char ch )

這是重載函數。

Prepends the byte ch 到此字節數組。

QByteArray &QByteArray:: prepend ( qsizetype count , char ch )

這是重載函數。

前置 count copies of byte ch 到此字節數組。

QByteArray &QByteArray:: prepend (const char * str )

這是重載函數。

Prepends the '\0'-terminated string str 到此字節數組。

QByteArray &QByteArray:: prepend (const char * str , qsizetype len )

這是重載函數。

前置 len bytes starting at str to this byte array. The bytes prepended may include '\0' bytes.

QByteArray &QByteArray:: prepend (const QByteArray & ba )

這是重載函數。

前置 ba 到此字節數組。

void QByteArray:: push_back (const QByteArray & other )

This function is provided for STL compatibility. It is equivalent to append( other ).

void QByteArray:: push_back ( char ch )

這是重載函數。

如同 append( ch ).

void QByteArray:: push_back (const char * str )

這是重載函數。

如同 append( str ).

`[since 6.0]` void QByteArray:: push_back ( QByteArrayView str )

這是重載函數。

如同 append( str ).

該函數在 Qt 6.0 引入。

void QByteArray:: push_front (const QByteArray & other )

This function is provided for STL compatibility. It is equivalent to prepend( other ).

void QByteArray:: push_front ( char ch )

這是重載函數。

如同 prepend( ch ).

void QByteArray:: push_front (const char * str )

這是重載函數。

如同 prepend( str ).

`[since 6.0]` void QByteArray:: push_front ( QByteArrayView str )

這是重載函數。

如同 prepend( str ).

該函數在 Qt 6.0 引入。

QByteArray::reverse_iterator QByteArray:: rbegin ()

返迴 STL-style reverse iterator pointing to the first byte in the byte-array, in reverse order.

警告： The returned iterator is invalidated on detachment or when the QByteArray 被修改。

另請參閱 begin (), crbegin ()，和 rend ().

QByteArray::const_reverse_iterator QByteArray:: rbegin () const

這是重載函數。

QByteArray &QByteArray:: remove ( qsizetype pos , qsizetype len )

移除 len bytes from the array, starting at index position pos , and returns a reference to the array.

若 pos is out of range, nothing happens. If pos is valid, but pos + len is larger than the size of the array, the array is truncated at position pos .

範例：

QByteArray ba("Montreal");
ba.remove(1, 4);
// ba == "Meal"

Element removal will preserve the array's capacity and not reduce the amount of allocated memory. To shed extra capacity and free as much memory as possible, call squeeze () after the last change to the array's size.

另請參閱 insert (), replace ()，和 squeeze ().

`[since 6.5]` QByteArray &QByteArray:: removeAt ( qsizetype pos )

Removes the character at index pos 。若 pos is out of bounds (i.e. pos >= size ()) this function does nothing.

This function was introduced in Qt 6.5.

另請參閱 remove ().

`[since 6.5]` QByteArray &QByteArray:: removeFirst ()

Removes the first character in this byte array. If the byte array is empty, this function does nothing.

This function was introduced in Qt 6.5.

另請參閱 remove ().

`[since 6.1]` template <typename Predicate> QByteArray &QByteArray:: removeIf ( Predicate pred )

Removes all bytes for which the predicate pred returns true from the byte array. Returns a reference to the byte array.

This function was introduced in Qt 6.1.

另請參閱 remove ().

`[since 6.5]` QByteArray &QByteArray:: removeLast ()

Removes the last character in this byte array. If the byte array is empty, this function does nothing.

This function was introduced in Qt 6.5.

另請參閱 remove ().

QByteArray::reverse_iterator QByteArray:: rend ()

返迴 STL-style reverse iterator pointing just after the last byte in the byte-array, in reverse order.

警告： The returned iterator is invalidated on detachment or when the QByteArray 被修改。

另請參閱 end (), crend ()，和 rbegin ().

QByteArray::const_reverse_iterator QByteArray:: rend () const

這是重載函數。

QByteArray QByteArray:: repeated ( qsizetype times ) const

Returns a copy of this byte array repeated the specified number of times .

若 times is less than 1, an empty byte array is returned.

範例：

QByteArray ba("ab");
ba.repeated(4);             // returns "abababab"

QByteArray &QByteArray:: replace ( qsizetype pos , qsizetype len , QByteArrayView after )

替換 len bytes from index position pos with the byte array after , and returns a reference to this byte array.

範例：

QByteArray x("Say yes!");
QByteArray y("no");
x.replace(4, 3, y);
// x == "Say no!"

另請參閱 insert () 和 remove ().

QByteArray &QByteArray:: replace ( qsizetype pos , qsizetype len , const char * after , qsizetype alen )

這是重載函數。

替換 len bytes from index position pos with alen bytes starting at position after . The bytes inserted may include '\0' bytes.

QByteArray &QByteArray:: replace ( char before , QByteArrayView after )

這是重載函數。

Replaces every occurrence of the byte before with the byte array after .

QByteArray &QByteArray:: replace (const char * before , qsizetype bsize , const char * after , qsizetype asize )

這是重載函數。

Replaces every occurrence of the bsize bytes starting at before 采用 asize bytes starting at after . Since the sizes of the strings are given by bsize and asize , they may contain '\0' bytes and do not need to be '\0'-terminated.

`[since 6.0]` QByteArray &QByteArray:: replace ( QByteArrayView before , QByteArrayView after )

這是重載函數。

Replaces every occurrence of the byte array before with the byte array after .

範例：

QByteArray ba("colour behaviour flavour neighbour");
ba.replace(QByteArray("ou"), QByteArray("o"));
// ba == "color behavior flavor neighbor"

該函數在 Qt 6.0 引入。

QByteArray &QByteArray:: replace ( char before , char after )

這是重載函數。

Replaces every occurrence of the byte before with the byte after .

void QByteArray:: reserve ( qsizetype size )

試圖分配內存為至少 size 字節。

If you know in advance how large the byte array will be, you can call this function, and if you call resize () often you are likely to get better performance.

If in doubt about how much space shall be needed, it is usually better to use an upper bound as size , or a high estimate of the most likely size, if a strict upper bound would be much bigger than this. If size is an underestimate, the array will grow as needed once the reserved size is exceeded, which may lead to a larger allocation than your best overestimate would have and will slow the operation that triggers it.

警告： reserve() reserves memory but does not change the size of the byte array. Accessing data beyond the end of the byte array is undefined behavior. If you need to access memory beyond the current end of the array, use resize ().

The sole purpose of this function is to provide a means of fine tuning QByteArray 's memory usage. In general, you will rarely ever need to call this function.

另請參閱 squeeze () 和 capacity ().

void QByteArray:: resize ( qsizetype size )

把字節數組的尺寸設為 size 字節。

若 size is greater than the current size, the byte array is extended to make it size bytes with the extra bytes added to the end. The new bytes are uninitialized.

若 size is less than the current size, bytes beyond position size are excluded from the byte array.

注意： While resize() will grow the capacity if needed, it never shrinks capacity. To shed excess capacity, use squeeze ().

另請參閱 size (), truncate ()，和 squeeze ().

`[since 6.4]` void QByteArray:: resize ( qsizetype newSize , char c )

把字節數組的尺寸設為 newSize 字節。

若 newSize is greater than the current size, the byte array is extended to make it newSize bytes with the extra bytes added to the end. The new bytes are initialized to c .

若 newSize is less than the current size, bytes beyond position newSize are excluded from the byte array.

注意： While resize() will grow the capacity if needed, it never shrinks capacity. To shed excess capacity, use squeeze ().

This function was introduced in Qt 6.4.

另請參閱 size (), truncate ()，和 squeeze ().

QByteArray QByteArray:: right ( qsizetype len ) const

Returns a byte array that contains the last len 字節對於此字節數組。

If you know that len cannot be out of bounds, use last () instead in new code, because it is faster.

返迴整個字節數組若 len 大於 size ().

返迴空 QByteArray if len is smaller than 0.

另請參閱 endsWith (), last (), first (), sliced (), chopped (), chop ()，和 truncate ().

QByteArray QByteArray:: rightJustified ( qsizetype width , char fill = ' ', bool truncate = false) const

Returns a byte array of size width 包含 fill byte followed by this byte array.

若 truncate is false and the size of the byte array is more than width , then the returned byte array is a copy of this byte array.

若 truncate is true and the size of the byte array is more than width , then the resulting byte array is truncated at position width .

範例：

QByteArray x("apple");
QByteArray y = x.rightJustified(8, '.');    // y == "...apple"

另請參閱 leftJustified ().

QByteArray &QByteArray:: setNum ( int n , int base = 10)

Represent the whole number n as text.

Sets this byte array to a string representing n in base base (ten by default) and returns a reference to this byte array. Bases 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

範例：

QByteArray ba;
int n = 63;
ba.setNum(n);           // ba == "63"
ba.setNum(n, 16);       // ba == "3f"

注意： The format of the number is not localized; the default C locale is used regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

另請參閱 number () 和 toInt ().

QByteArray &QByteArray:: setNum ( short n , int base = 10)

這是重載函數。

另請參閱 toShort ().

QByteArray &QByteArray:: setNum ( ushort n , int base = 10)

這是重載函數。

另請參閱 toUShort ().

QByteArray &QByteArray:: setNum ( uint n , int base = 10)

這是重載函數。

另請參閱 toUInt ().

QByteArray &QByteArray:: setNum ( long n , int base = 10)

這是重載函數。

另請參閱 toLong ().

QByteArray &QByteArray:: setNum ( ulong n , int base = 10)

這是重載函數。

另請參閱 toULong ().

QByteArray &QByteArray:: setNum ( qlonglong n , int base = 10)

這是重載函數。

另請參閱 toLongLong ().

QByteArray &QByteArray:: setNum ( qulonglong n , int base = 10)

這是重載函數。

另請參閱 toULongLong ().

QByteArray &QByteArray:: setNum ( float n , char format = 'g', int precision = 6)

這是重載函數。

Represent the floating-point number n as text.

Sets this byte array to a string representing n , with a given format and precision (with the same meanings as for QString::number (double, char, int)), and returns a reference to this byte array.

另請參閱 toFloat ().

QByteArray &QByteArray:: setNum ( double n , char format = 'g', int precision = 6)

這是重載函數。

Represent the floating-point number n as text.

另請參閱 toDouble () 和 QLocale::FloatingPointPrecisionOption .

QByteArray &QByteArray:: setRawData (const char * data , qsizetype size )

Resets the QByteArray to use the first size bytes of the data array. The bytes are not copied. The QByteArray will contain the data pointer. The caller guarantees that data will not be deleted or modified as long as this QByteArray and any copies of it exist that have not been modified.

This function can be used instead of fromRawData () to re-use existing QByteArray objects to save memory re-allocations.

另請參閱 fromRawData (), data ()，和 constData ().

void QByteArray:: shrink_to_fit ()

此函數為兼容 STL (標準模闆庫) 提供。它相當於 squeeze ().

QByteArray QByteArray:: simplified () const

Returns a copy of this byte array that has spacing characters removed from the start and end, and in which each sequence of internal spacing characters is replaced with a single space.

The spacing characters are those for which the standard C++ isspace() 函數返迴 true in the C locale; these are the ASCII characters tabulation '\t', line feed '\n', carriage return '\r', vertical tabulation '\v', form feed '\f', and space ' '.

範例：

QByteArray ba("  lots\t of\nwhitespace\r\n ");
ba = ba.simplified();
// ba == "lots of whitespace";

另請參閱 trimmed (), QChar::SpecialCharacter ，和 Spacing Characters .

qsizetype QByteArray:: size () const

返迴此字節數組的字節數。

The last byte in the byte array is at position size() - 1. In addition, QByteArray ensures that the byte at position size() is always '\0', so that you can use the return value of data () 和 constData () as arguments to functions that expect '\0'-terminated strings. If the QByteArray object was created from a raw data that didn't include the trailing '\0'-termination byte, then QByteArray doesn't add it automatically unless a 深拷貝被創建。

範例：

QByteArray ba("Hello");
qsizetype n = ba.size();    // n == 5
ba.data()[0];               // returns 'H'
ba.data()[4];               // returns 'o'
ba.data()[5];               // returns '\0'

另請參閱 isEmpty () 和 resize ().

`[since 6.0]` QByteArray QByteArray:: sliced ( qsizetype pos , qsizetype n ) const

Returns a byte array containing the n bytes of this object starting at position pos .

注意： 行為未定義當 pos < 0, n < 0, or pos + n > size ().

範例：

QByteArray x("Five pineapples");
QByteArray y = x.sliced(5, 4);     // y == "pine"
QByteArray z = x.sliced(5);        // z == "pineapples"

該函數在 Qt 6.0 引入。

另請參閱 first (), last (), chopped (), chop ()，和 truncate ().

`[since 6.0]` QByteArray QByteArray:: sliced ( qsizetype pos ) const

這是重載函數。

Returns a byte array containing the bytes starting at position pos in this object, and extending to the end of this object.

注意： 行為未定義當 pos < 0 or pos > size ().

該函數在 Qt 6.0 引入。

另請參閱 first (), last (), sliced (), chopped (), chop ()，和 truncate ().

QList < QByteArray > QByteArray:: split ( char sep ) const

Splits the byte array into subarrays wherever sep occurs, and returns the list of those arrays. If sep does not match anywhere in the byte array, split() returns a single-element list containing this byte array.

void QByteArray:: squeeze ()

Releases any memory not required to store the array's data.

The sole purpose of this function is to provide a means of fine tuning QByteArray 's memory usage. In general, you will rarely ever need to call this function.

另請參閱 reserve () 和 capacity ().

`[since 6.0]` bool QByteArray:: startsWith ( QByteArrayView bv ) const

返迴 true if this byte array starts with the sequence of bytes viewed by bv ；否則返迴 false .

範例：

QByteArray url("ftp://ftp.qt-project.org/");
if (url.startsWith("ftp:"))
    ...

該函數在 Qt 6.0 引入。

另請參閱 endsWith () 和 first ().

bool QByteArray:: startsWith ( char ch ) const

這是重載函數。

返迴 true if this byte array starts with byte ch ；否則返迴 false .

void QByteArray:: swap ( QByteArray & other )

交換字節數組 other with this byte array. This operation is very fast and never fails.

QByteArray QByteArray:: toBase64 ( QByteArray::Base64Options options = Base64Encoding) const

返迴字節數組的副本，編碼使用選項 options .

QByteArray text("Qt is great!");
text.toBase64();        // returns "UXQgaXMgZ3JlYXQh"
QByteArray text("<p>Hello?</p>");
text.toBase64(QByteArray::Base64Encoding | QByteArray::OmitTrailingEquals);      // returns "PHA+SGVsbG8/PC9wPg"
text.toBase64(QByteArray::Base64Encoding);                                       // returns "PHA+SGVsbG8/PC9wPg=="
text.toBase64(QByteArray::Base64UrlEncoding);                                    // returns "PHA-SGVsbG8_PC9wPg=="
text.toBase64(QByteArray::Base64UrlEncoding | QByteArray::OmitTrailingEquals);   // returns "PHA-SGVsbG8_PC9wPg"

The algorithm used to encode Base64-encoded data is defined in RFC 4648 .

另請參閱 fromBase64 ().

CFDataRef QByteArray:: toCFData () const

創建 CFData 從 QByteArray .

The caller owns the CFData object and is responsible for releasing it.

另請參閱 toRawCFData (), fromCFData (), fromRawCFData ()，和 fromRawData ().

double QByteArray:: toDouble ( bool * ok = nullptr) const

返迴字節數組被轉換成 double 值。

Returns an infinity if the conversion overflows or 0.0 if the conversion fails for other reasons (e.g. underflow).

若 ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

QByteArray string("1234.56");
bool ok;
double a = string.toDouble(&ok);   // a == 1234.56, ok == true
string = "1234.56 Volt";
a = str.toDouble(&ok);             // a == 0, ok == false

警告： The QByteArray content may only contain valid numerical characters which includes the plus/minus sign, the character e used in scientific notation, and the decimal point. Including the unit or additional characters leads to a conversion error.

注意： The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

此函數忽略前導和結尾空格。

另請參閱 number ().

`[since 6.5]` emscripten::val QByteArray:: toEcmaUint8Array ()

Creates a Uint8Array from a QByteArray .

This function transfers data from heap memory owned by a QByteArray to a JavaScript data buffer. The function allocates and copies into an ArrayBuffer, and returns a Uint8Array view to that buffer.

The JavaScript objects own a copy of the data, and this QByteArray can be safely deleted after the copy has been made.

QByteArray byteArray = "test";
emscripten::val uint8array = QByteArray::toEcmaUint8Array(byteArray);

This function was introduced in Qt 6.5.

另請參閱 toEcmaUint8Array().

float QByteArray:: toFloat ( bool * ok = nullptr) const

返迴字節數組被轉換成 float 值。

Returns an infinity if the conversion overflows or 0.0 if the conversion fails for other reasons (e.g. underflow).

若 ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

QByteArray string("1234.56");
bool ok;
float a = string.toFloat(&ok);    // a == 1234.56, ok == true
string = "1234.56 Volt";
a = str.toFloat(&ok);              // a == 0, ok == false

注意： The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

此函數忽略前導和結尾空格。

另請參閱 number ().

QByteArray QByteArray:: toHex ( char separator = '\0') const

Returns a hex encoded copy of the byte array.

The hex encoding uses the numbers 0-9 and the letters a-f.

若 separator is not '\0', the separator character is inserted between the hex bytes.

範例：

QByteArray macAddress = QByteArray::fromHex("123456abcdef");
macAddress.toHex(':'); // returns "12:34:56:ab:cd:ef"
macAddress.toHex(0);   // returns "123456abcdef"

另請參閱 fromHex ().

int QByteArray:: toInt ( bool * ok = nullptr, int base = 10) const

返迴字節數組被轉換成 int 使用基 base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

若 base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal (base 16); otherwise, if it begins with "0b", it is assumed to be binary (base 2); otherwise, if it begins with "0", it is assumed to be octal (base 8); otherwise it is assumed to be decimal.

返迴 0，若轉換失敗。

若 ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

QByteArray str("FF");
bool ok;
int hex = str.toInt(&ok, 16);     // hex == 255, ok == true
int dec = str.toInt(&ok, 10);     // dec == 0, ok == false

注意： The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

注意： Support for the "0b" prefix was added in Qt 6.4.

另請參閱 number ().

long QByteArray:: toLong ( bool * ok = nullptr, int base = 10) const

返迴字節數組被轉換成 long int using base base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

返迴 0，若轉換失敗。

若 ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

QByteArray str("FF");
bool ok;
long hex = str.toLong(&ok, 16);   // hex == 255, ok == true
long dec = str.toLong(&ok, 10);   // dec == 0, ok == false

注意： The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

注意： Support for the "0b" prefix was added in Qt 6.4.

另請參閱 number ().

qlonglong QByteArray:: toLongLong ( bool * ok = nullptr, int base = 10) const

返迴字節數組被轉換成 long long 使用基 base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

返迴 0，若轉換失敗。

若 ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

注意： The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

注意： Support for the "0b" prefix was added in Qt 6.4.

另請參閱 number ().

QByteArray QByteArray:: toLower () const

Returns a copy of the byte array in which each ASCII uppercase letter converted to lowercase.

範例：

QByteArray x("Qt by THE QT COMPANY");
QByteArray y = x.toLower();
// y == "qt by the qt company"

另請參閱 isLower (), toUpper ()，和 Character Case .

NSData *QByteArray:: toNSData () const

創建 NSData 從 QByteArray .

The NSData object is autoreleased.

另請參閱 fromNSData (), fromRawNSData (), fromRawData ()，和 toRawNSData ().

QByteArray QByteArray:: toPercentEncoding (const QByteArray & exclude = QByteArray(), const QByteArray & 包括 = QByteArray(), char percent = '%') const

Returns a URI/URL-style percent-encoded copy of this byte array. The percent parameter allows you to override the default '%' character for another.

By default, this function will encode all bytes that are not one of the following:

ALPHA ("a" to "z" and "A" to "Z") / DIGIT (0 to 9) / "-" / "." / "_" / "~"

To prevent bytes from being encoded pass them to exclude . To force bytes to be encoded pass them to include 。 percent character is always encoded.

範例：

QByteArray text = "{a fishy string?}";
QByteArray ba = text.toPercentEncoding("{}", "s");
qDebug("%s", ba.constData());
// prints "{a fi%73hy %73tring%3F}"

The hex encoding uses the numbers 0-9 and the uppercase letters A-F.

另請參閱 fromPercentEncoding () 和 QUrl::toPercentEncoding ().

CFDataRef QByteArray:: toRawCFData () const

Constructs a CFData that uses the bytes of the QByteArray .

The QByteArray 的字節不拷貝。

The caller guarantees that the QByteArray will not be deleted or modified as long as this CFData object exists.

另請參閱 toCFData (), fromRawCFData (), fromCFData ()，和 fromRawData ().

NSData *QByteArray:: toRawNSData () const

Constructs a NSData that uses the bytes of the QByteArray .

The QByteArray 的字節不拷貝。

The caller guarantees that the QByteArray will not be deleted or modified as long as this NSData object exists.

另請參閱 fromRawNSData (), fromNSData (), fromRawData ()，和 toNSData ().

short QByteArray:: toShort ( bool * ok = nullptr, int base = 10) const

返迴字節數組被轉換成 short 使用基 base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

返迴 0，若轉換失敗。

若 ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

注意： The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

注意： Support for the "0b" prefix was added in Qt 6.4.

另請參閱 number ().

std::string QByteArray:: toStdString () const

返迴 std::string 對象帶有的數據包含在此 QByteArray .

此運算符主要用於傳遞 QByteArray 到接受 std::string 對象的函數。

另請參閱 fromStdString () 和 QString::toStdString ().

uint QByteArray:: toUInt ( bool * ok = nullptr, int base = 10) const

返迴字節數組被轉換成 無符號 int 使用基 base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

返迴 0，若轉換失敗。

若 ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

注意： The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

注意： Support for the "0b" prefix was added in Qt 6.4.

另請參閱 number ().

ulong QByteArray:: toULong ( bool * ok = nullptr, int base = 10) const

返迴字節數組被轉換成 unsigned long int 使用基 base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

返迴 0，若轉換失敗。

若 ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

注意： The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

注意： Support for the "0b" prefix was added in Qt 6.4.

另請參閱 number ().

qulonglong QByteArray:: toULongLong ( bool * ok = nullptr, int base = 10) const

返迴字節數組被轉換成 unsigned long long 使用基 base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

返迴 0，若轉換失敗。

若 ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

注意： The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

注意： Support for the "0b" prefix was added in Qt 6.4.

另請參閱 number ().

ushort QByteArray:: toUShort ( bool * ok = nullptr, int base = 10) const

返迴字節數組被轉換成 unsigned short 使用基 base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

返迴 0，若轉換失敗。

若 ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

注意： The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

注意： Support for the "0b" prefix was added in Qt 6.4.

另請參閱 number ().

QByteArray QByteArray:: toUpper () const

Returns a copy of the byte array in which each ASCII lowercase letter converted to uppercase.

範例：

QByteArray x("Qt by THE QT COMPANY");
QByteArray y = x.toUpper();
// y == "QT BY THE QT COMPANY"

另請參閱 isUpper (), toLower ()，和 Character Case .

QByteArray QByteArray:: trimmed () const

Returns a copy of this byte array with spacing characters removed from the start and end.

範例：

QByteArray ba("  lots\t of\nwhitespace\r\n ");
ba = ba.trimmed();
// ba == "lots\t of\nwhitespace";

不像 simplified (), trimmed() leaves internal spacing unchanged.

另請參閱 simplified (), QChar::SpecialCharacter ，和 Spacing Characters .

void QByteArray:: truncate ( qsizetype pos )

截取字節數組按索引位置 pos .

若 pos 超越數組末尾，什麼都不發生。

範例：

QByteArray ba("Stockholm");
ba.truncate(5);             // ba == "Stock"

另請參閱 chop (), resize ()，和 first ().

bool QByteArray:: operator!= (const QString & str ) const

返迴 true if this byte array is not equal to the UTF-8 encoding of str ；否則返迴 false .

比較是區分大小寫的。

可以禁用此運算符通過定義 QT_NO_CAST_FROM_ASCII 當編譯應用程序時。那麼需要調用 QString::fromUtf8 (), QString::fromLatin1 ()，或 QString::fromLocal8Bit () explicitly if you want to convert the byte array to a QString before doing the comparison.

QByteArray &QByteArray:: operator+= (const QByteArray & ba )

追加字節數組 ba onto the end of this byte array and returns a reference to this byte array.

範例：

QByteArray x("free");
QByteArray y("dom");
x += y;
// x == "freedom"

若要追加到的字節數組非空，履行數據深拷貝，花費綫性時間 .

This operation typically does not suffer from allocation overhead, because QByteArray preallocates extra space at the end of the data so that it may grow without reallocating for each append operation.

另請參閱 append () 和 prepend ().

QByteArray &QByteArray:: operator+= ( char ch )

這是重載函數。

Appends the byte ch onto the end of this byte array and returns a reference to this byte array.

QByteArray &QByteArray:: operator+= (const char * str )

這是重載函數。

Appends the '\0'-terminated string str onto the end of this byte array and returns a reference to this byte array.

bool QByteArray:: operator< (const QString & str ) const

返迴 true if this byte array is lexically less than the UTF-8 encoding of str ；否則返迴 false .

比較是區分大小寫的。

bool QByteArray:: operator<= (const QString & str ) const

返迴 true if this byte array is lexically less than or equal to the UTF-8 encoding of str ；否則返迴 false .

比較是區分大小寫的。

QByteArray &QByteArray:: operator= (const QByteArray & other )

賦值 other 到此字節數組，並返迴此字節數組的引用。

QByteArray &QByteArray:: operator= (const char * str )

這是重載函數。

賦值 str 到此字節數組。

QByteArray &QByteArray:: operator= ( QByteArray && other )

移動賦值 other 到此 QByteArray 實例。

bool QByteArray:: operator== (const QString & str ) const

返迴 true if this byte array is equal to the UTF-8 encoding of str ；否則返迴 false .

比較是區分大小寫的。

bool QByteArray:: operator> (const QString & str ) const

返迴 true if this byte array is lexically greater than the UTF-8 encoding of str ；否則返迴 false .

比較是區分大小寫的。

bool QByteArray:: operator>= (const QString & str ) const

返迴 true if this byte array is greater than or equal to the UTF-8 encoding of str ；否則返迴 false .

比較是區分大小寫的。

char &QByteArray:: operator[] ( qsizetype i )

返迴字節按索引位置 i 作為可修改引用。

i 必須是字節數組中的有效索引位置 (即 0 <= i < size ()).

範例：

QByteArray ba("Hello, world");
cout << ba[0]; // prints H
ba[7] = 'W';
// ba == "Hello, World"

另請參閱 at ().

char QByteArray:: operator[] ( qsizetype i ) const

這是重載函數。

如同 at( i ).

宏文檔編製

QByteArrayLiteral ( ba )

宏生成數據為 QByteArray 從字符串文字 ba 在編譯時。創建 QByteArray 是自由的在此情況下，且生成的字節數組數據是存儲在編譯對象文件的隻讀段中。

例如：

QByteArray ba = QByteArrayLiteral("byte array contents");

使用 QByteArrayLiteral 而不是帶雙引號的純 C++ 字符串文字可以顯著加速創建 QByteArray 實例從編譯時的已知數據。

另請參閱 QStringLiteral .

QT_NO_CAST_FROM_BYTEARRAY

禁用自動轉換從 QByteArray 到 const char * 或 const void *。

另請參閱 QT_NO_CAST_TO_ASCII and QT_NO_CAST_FROM_ASCII .

QByteArray 類

公共類型

公共函數

靜態公共成員

相關非成員

宏

詳細描述

最大尺寸和內存不足情況

C locale and ASCII functions

C Strings

Spacing Characters

數字字符串轉換

Character Case

成員類型文檔編製

enum QByteArray:: Base64Option flags QByteArray:: Base64Options

QByteArray:: const_iterator

QByteArray:: const_reverse_iterator

QByteArray:: iterator

QByteArray:: reverse_iterator

成員函數文檔編製

const char *QByteArray:: operator const char * () const

const void *QByteArray:: operator const void * () const

[static] QByteArray::FromBase64Result QByteArray:: fromBase64Encoding ( QByteArray && base64 , QByteArray::Base64Options options = Base64Encoding)

[static] QByteArray::FromBase64Result QByteArray:: fromBase64Encoding (const QByteArray & base64 , QByteArray::Base64Options options = Base64Encoding)

[constexpr] QByteArray:: QByteArray ()

QByteArray:: QByteArray (const char * data , qsizetype size = -1)

QByteArray:: QByteArray ( qsizetype size , char ch )

QByteArray:: QByteArray ( qsizetype size , Qt::Initialization )

QByteArray:: QByteArray (const QByteArray & other )

QByteArray:: QByteArray ( QByteArray && other )

QByteArray:: ~QByteArray ()

QByteArray &QByteArray:: append (const QByteArray & ba )

QByteArray &QByteArray:: append ( char ch )

QByteArray &QByteArray:: append ( qsizetype count , char ch )

QByteArray &QByteArray:: append (const char * str )

QByteArray &QByteArray:: append (const char * str , qsizetype len )

QByteArray &QByteArray:: append ( QByteArrayView data )

char QByteArray:: at ( qsizetype i ) const

char QByteArray:: back () const

char &QByteArray:: back ()

QByteArray::iterator QByteArray:: begin ()

QByteArray::const_iterator QByteArray:: begin () const

qsizetype QByteArray:: capacity () const

QByteArray::const_iterator QByteArray:: cbegin () const

QByteArray::const_iterator QByteArray:: cend () const

void QByteArray:: chop ( qsizetype n )

QByteArray QByteArray:: chopped ( qsizetype len ) const

void QByteArray:: clear ()

[since 6.0] int QByteArray:: compare ( QByteArrayView bv , Qt::CaseSensitivity cs = Qt::CaseSensitive) const

QByteArray::const_iterator QByteArray:: constBegin () const

const char *QByteArray:: constData () const

QByteArray::const_iterator QByteArray:: constEnd () const

[since 6.0] bool QByteArray:: contains ( QByteArrayView bv ) const

bool QByteArray:: contains ( char ch ) const

[since 6.0] qsizetype QByteArray:: count ( QByteArrayView bv ) const

qsizetype QByteArray:: count ( char ch ) const

QByteArray::const_reverse_iterator QByteArray:: crbegin () const

QByteArray::const_reverse_iterator QByteArray:: crend () const

char *QByteArray:: data ()

const char *QByteArray:: data () const

QByteArray::iterator QByteArray:: end ()

QByteArray::const_iterator QByteArray:: end () const

[since 6.0] bool QByteArray:: endsWith ( QByteArrayView bv ) const

bool QByteArray:: endsWith ( char ch ) const

[since 6.1] QByteArray::iterator QByteArray:: erase ( QByteArray::const_iterator first , QByteArray::const_iterator last )

[since 6.5] QByteArray::iterator QByteArray:: erase ( QByteArray::const_iterator it )

QByteArray &QByteArray:: fill ( char ch , qsizetype size = -1)

[since 6.0] QByteArray QByteArray:: first ( qsizetype n ) const

[static] QByteArray QByteArray:: fromBase64 (const QByteArray & base64 , QByteArray::Base64Options options = Base64Encoding)

[static] QByteArray QByteArray:: fromCFData ( CFDataRef data )

[static, since 6.5] QByteArray QByteArray:: fromEcmaUint8Array ( emscripten::val uint8array )

[static] QByteArray QByteArray:: fromHex (const QByteArray & hexEncoded )

[static] QByteArray QByteArray:: fromNSData (const NSData * data )

[static] QByteArray QByteArray:: fromPercentEncoding (const QByteArray & input , char percent = '%')

[static] QByteArray QByteArray:: fromRawCFData ( CFDataRef data )

[static] QByteArray QByteArray:: fromRawData (const char * data , qsizetype size )

[static] QByteArray QByteArray:: fromRawNSData (const NSData * data )

[static] QByteArray QByteArray:: fromStdString (const std::string & str )

char QByteArray:: front () const

char &QByteArray:: front ()

enum QByteArray:: Base64Option
flags QByteArray:: Base64Options

const char QByteArray:: operator const char () const

const void QByteArray:: operator const void () const

`[static]` QByteArray::FromBase64Result QByteArray:: fromBase64Encoding ( QByteArray && base64 , QByteArray::Base64Options options = Base64Encoding)

`[static]` QByteArray::FromBase64Result QByteArray:: fromBase64Encoding (const QByteArray & base64 , QByteArray::Base64Options options = Base64Encoding)

`[constexpr]` QByteArray:: QByteArray ()

`[since 6.0]` int QByteArray:: compare ( QByteArrayView bv , Qt::CaseSensitivity cs = Qt::CaseSensitive) const

`[since 6.0]` bool QByteArray:: contains ( QByteArrayView bv ) const

`[since 6.0]` qsizetype QByteArray:: count ( QByteArrayView bv ) const

`[since 6.0]` bool QByteArray:: endsWith ( QByteArrayView bv ) const

`[since 6.1]` QByteArray::iterator QByteArray:: erase ( QByteArray::const_iterator first , QByteArray::const_iterator last )

`[since 6.5]` QByteArray::iterator QByteArray:: erase ( QByteArray::const_iterator it )

`[since 6.0]` QByteArray QByteArray:: first ( qsizetype n ) const

`[static]` QByteArray QByteArray:: fromBase64 (const QByteArray & base64 , QByteArray::Base64Options options = Base64Encoding)

`[static]` QByteArray QByteArray:: fromCFData ( CFDataRef data )

`[static, since 6.5]` QByteArray QByteArray:: fromEcmaUint8Array ( emscripten::val uint8array )

`[static]` QByteArray QByteArray:: fromHex (const QByteArray & hexEncoded )

`[static]` QByteArray QByteArray:: fromNSData (const NSData * data )

`[static]` QByteArray QByteArray:: fromPercentEncoding (const QByteArray & input , char percent = '%')

`[static]` QByteArray QByteArray:: fromRawCFData ( CFDataRef data )

`[static]` QByteArray QByteArray:: fromRawData (const char * data , qsizetype size )

`[static]` QByteArray QByteArray:: fromRawNSData (const NSData * data )

`[static]` QByteArray QByteArray:: fromStdString (const std::string & str )

`[since 6.0]` qsizetype QByteArray:: indexOf ( QByteArrayView bv , qsizetype from = 0) const

`[since 6.0]` QByteArray &QByteArray:: insert ( qsizetype i , QByteArrayView data )

`[since 6.3]` bool QByteArray:: isValidUtf8 () const

`[since 6.0]` QByteArray QByteArray:: last ( qsizetype n ) const

`[since 6.0]` qsizetype QByteArray:: lastIndexOf ( QByteArrayView bv , qsizetype from ) const

`[since 6.2]` qsizetype QByteArray:: lastIndexOf ( QByteArrayView bv ) const

`[static]` QByteArray QByteArray:: number ( int n , int base = 10)

`[static]` QByteArray QByteArray:: number ( uint n , int base = 10)

`[static]` QByteArray QByteArray:: number ( long n , int base = 10)

`[static]` QByteArray QByteArray:: number ( ulong n , int base = 10)

`[static]` QByteArray QByteArray:: number ( qlonglong n , int base = 10)

`[static]` QByteArray QByteArray:: number ( qulonglong n , int base = 10)

`[static]` QByteArray QByteArray:: number ( double n , char format = 'g', int precision = 6)

`[since 6.4]` QByteArray QByteArray:: percentDecoded ( char percent = '%') const

`[since 6.0]` void QByteArray:: push_back ( QByteArrayView str )

`[since 6.0]` void QByteArray:: push_front ( QByteArrayView str )

`[since 6.5]` QByteArray &QByteArray:: removeAt ( qsizetype pos )

`[since 6.5]` QByteArray &QByteArray:: removeFirst ()

`[since 6.1]` template <typename Predicate> QByteArray &QByteArray:: removeIf ( Predicate pred )

`[since 6.5]` QByteArray &QByteArray:: removeLast ()

`[since 6.0]` QByteArray &QByteArray:: replace ( QByteArrayView before , QByteArrayView after )

`[since 6.4]` void QByteArray:: resize ( qsizetype newSize , char c )